/save-all flush causes server to freeze and finally crash

Calling 'save-all flush' might sometimes cause the server to freeze resulting in a timeout for the player before finally crashing the server

Sequence of events as shown in the log:

[12:49:27 INFO]: <Player> \save-all flush
[12:49:31 WARN]: Trying to add entity with duplicated UUID d2ed2b6f-4c8f-45b2-854f-c45271da95b0. Existing minecraft:strider#664, new: minecraft:strider#677
[12:49:51 INFO]: ThreadedAnvilChunkStorage (world): All chunks are saved
[12:50:42 FATAL]: A single server tick took 60.00 seconds (should be max 0.05)
[12:50:42 FATAL]: Considering it to be crashed, server will forcibly shutdown.
[12:50:42 ERROR]: This crash report has been saved to: ...